Imagine for a moment you are one of Novak Djokovic, Andy Murray or Roger
Federer tuning in to the final of the BNP Paribas Open on Sunday. You watch
Rafael Nadal, apparently on the ropes against the hardest forehand in
tennis, recover to break the resilience of his opponent, Juan Martín del
Potro, and complete the day with his incisors embedded in another trophy.

Do you feel pleasure that Nadal is back — Federer kept insisting that he was,
though he may have been joking — or might you silently curse? Or do you
count your blessings and your grand-slam titles (Federer